Page 23 - 2023外研科学重点书目

规模宏大
Black Hole Explosions? 黑洞爆炸?
收录 1869 年—2007 S. W. Hawking 霍金
年期间经典文献 800 Editor’s Note 编者按
It was realized more than two hundred years ago that there is a critical mass and radius beyond
which light cannot escape the gravitational field of an object—such an object becomes a “black 人们在两百多年前就已经意识到，对于给定的半径有一个临界质量，当物体的质量
超出临界质量时，其引力场就强到甚至连光都不能逃脱——这样的物体变成了“黑
余篇 hole”. This idea was rigorously validated by the theory of general relativity. Here Stephen 洞”。这一想法在广义相对论中得到了严格验证。本文中，斯蒂芬 · 霍金向我们表明
Hawking shows that black holes have effective temperatures that are inversely related to their
黑洞有跟其质量成反比的等效温度，因此它必须从其事件视界向外辐射光子和中微
mass, and should therefore radiate photons and neutrinos from their event horizons—they are
not fully “black”. As this radiation proceeds, the black hole loses mass. Finally it emits large 子——即它们并不完全是“黑”的。黑洞在辐射过程中会损失质量，最终释放出大
quantities of X-rays and gamma-rays, and disappears in an explosion. “Hawking radiation” from 量的 X 射线和伽玛射线，并在一次爆炸之后消失。虽然目前还没有直接观测到，但
专业导读
black holes is now widely expected, but has not yet been seen. 人们普遍相信黑洞存在“霍金辐射”。
UANTUM gravitational effects are usually ignored in calculations of the formation 在计算黑洞的形成和演化时，一般可忽略量子引力效应。这一点的合理性在于，
Qand evolution of black holes. The justification for this is that the radius of curvature
of space-time outside the event horizon is very large compared to the Planck length 在事件视界外的时空曲率半径远大于普朗克长度 (Gh/c 3 ) 1/2 ≈ 10 –33 cm，而在此尺度上 《自然》杂志的资深编
(Gh/c 3 ) 1/2 ≈10 –33 cm, the length scale on which quantum fluctuations of the metric are 预期度规的量子涨落是 1 的量级。这意味着由引力场产生的粒子的能量密度和时空
expected to be of order unity. This means that the energy density of particles created 曲率相比要小。虽然量子效应在局部很小，然而它们仍然可能在宇宙的寿命≈ 10 17 s
by the gravitational field is small compared to the space-time curvature. Even though 内积累产生重大的影响，这个时间远长于普朗克时间≈ 10 –43 s。这篇快报的目的是说
经典文献 quantum effects may be small locally, they may still, however, add up to produce a 明，似乎任何黑洞都将以预期的速率产生和发射粒子，如中微子或光子，正如同黑 辑通力合作，撰写文章
significant effect over the lifetime of the Universe ≈ 10 17 s which is very long compared
to the Planck time ≈10 –43 s. The purpose of this letter is to show that this indeed may
be the case: it seems that any black hole will create and emit particles such as neutrinos 洞是一个温度为 (κ/2π)(h/2k) ≈ 10 –6 (M ⊙/M ) K 的物体所表现的那样，其中 κ 是黑洞的
表面引力 [1] 。当黑洞发射这类热辐射时，我们预期它将损失质量。这本身将增大它
or photons at just the rate that one would expect if the black hole was a body with a 的表面引力，因而增大其发射速率。从此，黑洞将具有 10 71 (M ⊙ /M ) –3 s 量级的有限 导读，帮助读者快速了
荟萃《自然》创刊以来 temperature of (κ/2π) (h/2k) ≈10 –6 (M /M)K where κ is the surface gravity of the black 寿命。对于太阳质量的黑洞，这将比宇宙年龄更长。然而，可能存在许多较小的黑
hole 1 . As a black hole emits this thermal radiation one would expect it to lose mass. This
in turn would increase the surface gravity and so increase the rate of emission. The black 洞，它们是由早期宇宙中的涨落形成的 [2] 。任何这类质量小于 10 15 g 的黑洞到现在都
hole would therefore have a finite life of the order of 10 71 (M /M) –3 s. For a black hole of 应该蒸发殆尽了。在接近它生命终了时，其粒子发射速率将非常高，在最后 0.1 s 将 解文章大意
极具开创意义与影响力 solar mass this is much longer than the age of the Universe. There might, however, be 释放约 10 30 erg 能量。以天文学的标准来看，这是一个相当小的爆炸，但它相当于大
much smaller black holes which were formed by fluctuations in the early Universe 2 . Any
such black hole of mass less than 10 15 g would have evaporated by now. Near the end of 约一百万个 100 万吨量级的氢弹爆炸。
its life the rate of emission would be very high and about 10 30 erg would be released in the
的经典文献 last 0.1 s. This is a fairly small explosion by astronomical standards but it is equivalent to
about 1 million 1 Mton hydrogen bombs.
To see how this thermal emission arises, consider (for simplicity) a massless Hermitean 为了解释黑洞热辐射是如何产生的，为简单起见，在一个包含由一颗恒星塌缩
scalar field φ which obeys the covariant wave equation φ ; abg ab = 0 in an asymptotically 形成的一个黑洞的渐近平直时空中，考虑一个无质量的厄米标量场 φ，且它遵守协
flat space time containing a star which collapses to produce a black hole. The Heisenberg
operator φ can be expressed as 变波动方程 φ ; ab g ab = 0。海森堡算符 φ 可表示为：
578 579 英汉对照
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zw31-45.indd 578 2014.4.24 10:13:12 AMzw31-45.indd 579 2014.4.24 10:13:12 AM
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